Minnesota consists of USDA hardiness zones 3 to 5. There are many varieties of Dutch iris bulbs and some are hardy in those zones. For example, the "Eye of the Tiger" Dutch iris is hardy in zones 4 to 9 and the "Royal Yellow" Dutch iris is hardy in zones 3 to 8. Always follow the recommended zones and planting instructions that come with your plant; however, most Dutch iris bulbs are planted in a similar manner.
Choose when to plant your bulbs. September is the ideal time to plant Dutch iris bulbs in Minnesota. The bulbs need a few weeks to get established and settle in before the harsh winter arrives.
Choose a location in full sun and improve the soil conditions by tilling the top foot of your soil with a hoe, garden rake or tiller. Then mix in 3 or 4 inches of peat moss, compost or similar organic matter.
Dig holes that are as wide as the iris bulbs, but about 4 inches deeper than the bulbs are long. Space multiple Dutch iris bulbs 3 inches apart.
Set one bulb in each hole so that the tip is facing up and back fill the soil. Pack down the soil lightly with your hands.
Water the area with about 1 to 2 inches of water. Water slowly and so that no puddles form.
Spread the area with 4 to 6 inches of mulch, such as straw or bark. This will help keep the soil warmer during Minnesota's cold winter months.